I'm a fan of Beaty's work from 1998. Nothing I've seen has been as easy to implement: leaving space in front of each car creates smooth motion.

https://trafficwaves.org/trafexp.html or easier at https://web.archive.org/web/20260114173129/https://trafficwa...

https://web.archive.org/web/20251214172912/http://trafficwav... has some nice visualizations.

MIT got more press when they "rediscovered" this in 2017:

https://people.csail.mit.edu/bkph/Traffic_Flow_Animation

I'm a car fan, so I'd rather reward drivers for optimal behaviors vs broad car-reductions. I'll probably turn out to be on the wrong side, but maybe we'll find a good compromise.